Defrosting means for refrigerating apparatus



May 17, 1955 L. A. PHlLlPP DEFROSTING MEANS FOR REFRIGERATING APPARATUS2 Sheets-Sheet 1 Filed Nov. 2, 1951 m m w m A" PHIL/PP W Z M mumm- BYlrroR/vcy May 17, 1955 L. A. PHILIPP 2,708,348

DEFROSTING MEANS FOR REFRIGERATING APPARATUS Filed Nov. 2, 1951 2Sheets-Sheet 2 INVENTOR. [Amen/c5 A Plum 19 rromvry United States Patent()fi DEFROSTING MEANS FOR REFRIGERATING APPARATUS Lawrence A. Philipp,Detroit, Mich., assignors to Nash- Ke lvinator Corporation, Detroit,Mich., a corporation of Maryland Application November 2, 1951, SerialNo. 254,466 4 Claims. (Cl. 62-4) This invention relates to refrigeratingapparatus and more particularly to an arrangement for defrosting arefrigerant evaporator thereof.

One of the objects of the present invention is to provide forrefrigerating systems an improved arrangement for rapidly defrosting arefrigerant evaporator of said system by applying extraneous heat to theliquid refrigerant in the evaporator and at the same time by-passing therefrigerant condenser of said system to conduct the hot gaseousrefrigerant from the refrigerant circulating element or compressordirectly into the evaporator and to limit the application of such heatand the flow of said gaseous refrigerant to periods when saidrefrigerant circulating element or compressor of said system is inoperation.

In carrying out the aforesaid object, it is a further object to initiatethe application of heat and the flow of such gaseous refrigerant inresponse to a predetermined number of cycles of the refrigerantcirculating element or by a timing device, and to further control suchapplication of heat and flow of refrigerant so that such application andflow takes place only during periods when the refrigerant circulatingelement is in operation.

Another object of my invention is to provide a new method for defrostinga refrigerating system by utilizing the hot gases leaving the compressorand at the same time using extraneous heat by applying same to theliquid refrigerant in the evaporator of said system. Another object ofmy invention is to provide an improved arrangement for defrosting arefrigerant evaporator by passing hot gases from the motor-compressorunit of a refrigerating system directly into the evaporator thereofwherein said gases are condensed, and to apply extraneous heat to thecondensed liquid in said evaporator to aid in defrosting the evaporator.

Another object of my invention is to provide an improved arrangement fordefrosting a refrigerant evaporator by passing hot refrigerant gasesfrom the motorcompressor unit of a refrigerating system directly intothe evaporator thereof wherein said gases are condensed, and to applyextraneous heat to the condensed liquid in said evaporator to aid indefrosting the evaporator, and to limit the fiow of said hot gases intothe evaporator and such application of extraneous heat to periods whenthe motor-compressor unit isin operation.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein preferred forms of the present invention are clearlyshown.

In the drawings:

Fig. l is a front view of a refrigerator embodying features of myinvention and showing a portion thereof broken away;

Fig. 2 is a side view of the refrigerator showing a portion thereofbroken away;

Fig. 3 is an isometric illustration of a refrigerant evaporatorembodying features of my invention and shown removed from therefrigerator shown in Figs. 1 and 2;

Fig. 4 is a view of part of the evaporator taken along the line 4 4 ofFig. 3;

Fig. 5 is a diagrammatic illustration of the system embodying featuresof my invention, with an isometric illustration of the evaporator; and

Fig. 6 is a diagrammatic illustration of a portion of the system shownin Fig. 5 and showing a modified arrangement of control embodyingfeatures of my inven tion.

In accordance with my invention, I provide an arrangement for arefrigerating system for rapidly defrosting the refrigerant evaporatorthereof. The refrigcrating system includes a motor-compressor unit, acondenser and evaporator operatively connected together so that duringnormal operation the system cycles in re sponse to changes oftemperature in the refrigerant evaporator. This type of system is wellknown and used extensively at the present time. In such system, a smalldiameter capillary tube is used to control the flow of liquidrefrigerant from the condenser to the evaporator. The gaseousrefrigerant is evaporated in said evaporator and conducted from theevaporator to the motor-compressor unit through a vapor return conduit.The motor-compressor unit compresses the gaseous refrigerant anddelivers the hot gaseous refrigerant to the condenser wherein it isliquefied and from which it is delivered to the small diameter orcapillary tube. in the arrangement for defrosting, I utilize the hotgaseous refrigerant flowing from the motor-compressor unit by conductingsame directly into the evaporator and bypassing the condenser of therefrigerating system. This is accomplished by means of a bypass conduitwhich is normally closed by a solenoid valve but open during the periodof defrosting to permit the refrigerant to by-pass the condenser andcapillary tube so that the hot gaseous refrigerant flows directly intothe evaporator. This hot gaseous refrigerant, when coming into contactwith the interior of the refrigerant evaporator, condenses, due to thetemperature of the walls of the evaporator which walls collect frost andice thereon during normal operation of the system. The condensedrefrigerant is at this time forced ahead of the gaseous refrigerant intothe accumulator of the evaporator. Furthermore, I provide for applyingextraneous heat to the liquid refrigerant condensed in the evaporatorand confined in the accumulator therein at the time the hot gases arebeing sent directly into the evaporator. With the combination of hotgaseous refrigerant being passed directly into the evap- ,orator,wherein such condenses, and by applying extraneous heat to suchcondensed refrigerant to evaporate the condensed refrigerant and tofurther raise the temperature of the evaporator and pressure therein,defrosting rapidly takes place so that frozen foods and the like storedtherein do not have an opportunity to warm up sufiiciently to meltbefore the defrosting phase has been completed and the refrigeratingsystem is back in normal operation. In addition, I have provided forcontrolling the flow of hot gaseous refrigerant through the by-passconduit and the operation of the heating element so that the same onlycome into operation after a predetermined number of cycles of therefrigerating systern or by a timing device so as to provide automaticoperation. When defrosting takes place after a predetermined number ofcycles 1 have arranged to further control such application of heat andflow of hot gases in accordance with changes in temperatures of theevaporator so that such application and flow take place only duringperiods when the temperature of the evaporator is above a certain valueand when the motor-compressor unit is in operation.

Referring to the drawings, the numeral 2% designates, in general, arefrigerator cabinet. Within the upper portion of the cabinet there ispositioned a refrigerant evaporator 22 and in the lower portion of thecabinet there is positioned a refrigerant condensing or circulatingelement 24. Refrigerant supply and return conduits 26 and 28respectively operatively connect the evaporator and the condensingelement together.

The cabinet comprises, in general, an outer casing 3t and an inner liner32. These are made in box-like formation of sheet metal such, forexample, as sheet steel, and are spaced apart allowing for suitablespace for insulation 34 between the cssing and liner walls. At the frontof the cabinet, heat breaker strips 36 span the edges of the liner andcasing and also serve as a finish strip around an access opening to thecabinet. A suitably constructed door 38 is provided to close the accessopening and may be hinged to one side wall of the cabinet. Immediatelybelow the door 38, a second door 40 is provided which closes the frontof a machinery compartment 42 wherein the condensing element 24 ishoused. This compartment 42 is in open communication at the rear thereofwith a flue 44 which induces upward draft of air through the compartmentto aid cooling of the condensing element 24.

The liner 32 forms walls of a food storage compartment 46 and of afreezing compartment 48 which are separated by a horizontal partition orair baffie 49. Arranged immediately below the evaporator 22, the baffle49 is spaced from the cabinet door and rear wall to allow for limitedair circulation between the evaporator and food storage compartment tocool the latter. Below the bafile 9, a number of shelves 543 may besuitably arranged and be supported on the liner sides. The baflle 49also functions as a drip baflle for the defrosting operation and may beprovided with a drain aperture to discharge into a removable container51 which may be supported in the uppermost of the shelves 50.

Preferably, the evaporator 22 is of the so-called dry expansion typecomprising, a refrigerant coil or conduit S2 and a heat absorbing member54 in the form of a box-shaped container. The container 54 extendssubstantially from the door 38 to the liner rear wall and substantiallyto the liner side walls to provide a large heat absorbing surface andalso to provide a large storage space for ice cubes, foods to be frozen,etc. A door 56 preferably closes the front of the container 54 to avoidloss of cold air therefrom when the outer door 38 of the refrigerator isopened.

As shown in Fig. 3, the evaporator coil 52 is wrapped in helicalformation crosswise about the container 54 to extend along the top,bottom and sides thereof. Any suitable securing means, such asbituminous cement, may be used to secure the coil 52 in intimate contactwith the container walls to obtain etiicicnt transfer of heat from thecontainer to the refrigerant or the same may be secured together byfusion.

On the rear wall of the container 54 is a refrigerant accumulator 6%which be of tubular form and may extend longitudinally between the sidesof the container or crosswise thereof. One end, as at 62, of theaccumulator 62 is connected to the discharge end of the evaporator coil52, and the other end, as at 64, of the accumulator is connected to thegaseous refrigerant return conduit 28.

The refrigerant condensing element 24 may be of conventional type havinga motor-compressor unit 66 which generates heat and a finned condenser68 which dissipates heat. The return conduit 28 is connected to themotor-compressor unit 66, and the refrigerant supply conduit 26 isconnected to the condenser 68. A conduit 7:"; connects themotor-compressor outlet to the inlet of the condenser 68. Asillustrated, the refrigerant supply conduit 26 is preferably a smalldiameter 4 or capillary tube arranged to control the flow of liquidrefrigerant to the evaporator coil 52.

A thermostat 72 is provided for controlling cycling operation of thesystem in response to changes in tem perature of the evaporator 22 tomaintain desired evaporator 22 and compartment 46 temperatures. Thethermostat '72 may be of the well-known type comprising, in general, asnap-acting switch '74 and a switch actuator or bellows 76, a conduitand bulb 82. These form a closed system which may be charged with any ofthe well-known temperature responsive, eXpansible-contractable fluids. Aconnecting rod 84 operatively connects a movable end of the bellows 76and the switch '74 together. The switch 74 comprises the usual movableswitch mechanism 86, movable contact 88 and fixed contact 90.

The electric motor of the motor-compressor unit 66 and thermostaticswitch 74 are electrically connected by lead wires 92, 94 and 96. Thecircuit through the thermostatic switch and motor is wires 92, 94,contacts 99, 88, and wire 96. Lead wires 92 and 96 may be connected toany suitable source of electrical energy.

During normal operation, the thermostat controls the cycling of therefrigerating system. When there is a de mand for refrigeration thethermostat closes contacts 88 and of switch '74 to close the circuit tothe motorcornpressor unit. This demand occurs when the tern perature ofthe evaporator 22 reaches a predetermined high value to thus causebellows 76 to expand and close contacts 88 and 99 and said circuit. Whenthe temperature of the evaporator 22 reaches a predetermined low valuethe bellows 76 contracts to actuate switch 74 to open the said contactsand circuit to the motor-compressor. During such normal operation,liquid refrigerant is delivered from the condenser 68 to the evaporator22 under the control of the small diameter or capillary tube 26. Withinthe evaporator the liquid is evaporated and from which it is conductedto the compressor through the vapor return conduit 28. The compressorcompresses the refrigerant and delivers the same to the condenserwherein it is liquefied and from which it is delivered to the tube 26.During operation some liquid refrigerant is conducted into therefrigerant accumulator 60 as shown at 97, which is large enough toprevent any refrigerant passing into the return conduit 28. In chargingthe system with refrigerant, the proper amount is introduced thereintoso that some liquid will go into the accumulator during operation butnone will fiow therefrom. During operation, gaseous refrigerant iswithdrawn from the upper region of the accumulator 6t and returned tothe motor-compressor unit through the return conduit 28.

To provide for rapidly defrosting the evaporator 22 from ice and frostwhich collects thereon during normal operation, I provide a refrigerantbypass conduit to deliver hot gaseous refrigerant directly from themotorcompressor unit into the evaporator 22 during defrosting operation,and I provide an extraneous source of heat or electric heater 104 toheat the accumulator 6t) and liquid contained therein during such periodof defrosting.

The by-passed conduit 1% by-passes the refrigerant condenser and isillustrated as being connected at one end, as at 196, to the conduit 7%ahead of the inlet to the condenser. The other end of the by-passedconduit 1% is connected to the refrigerant evaporator coil 52. As shown,the by-passed conduit is much larger than the capillary tube whichnormally controls the flow of liquid refrigerant to the evaporator sothat on defrosting, gaseous refrigerant is free to flow directly throughthe by-passed conduit into the evaporator without any reduction inpressure to the extent which would result in expansion upon theadmission of such refrigerant into the evaporator 22. A valve 108 ispositioned in conduit Tilt) and maintains said conduit closed to theflow of refrigerant therethrough during normal operation and is moved toopen position during defrosting of the evaporator to allow the flow ofgaseous refrigerant through said conduit 100. This valve is preferablyan electrically operated solenoid valve but may be of any other suitabletype or otherwise suitably controlled.

The heater 104 may be held by a clamp 110 to a flange 112 of theaccumulator 60 as shown in detail in Fig. 4. The accumulator flange 112may be formed with a groove 114 to receive the heating element 104 so asto obtain large surface contact therewith to provide high heat transfertherebetween. Screws 116 or other suitable securing means may be used tosecure the clamp 110 to the accumulator flange and hold the heatingelement in heat conducting relationship therewith.

In order to provide for automatic defrosting any suitable counting ortiming device now in use or known in the art may be used in order tocontrol the energization of the heating element 104 and the operation ofthe valve 108. In Fig. 5 I have shown a counting device 120 which isactuated by the connecting rod 84 of the thermostatic switch 72. On thelower part of the connecting rod 84 is provided a pawl or finger 122which engages teeth 124 of ratchet wheel 126. The counting member isprovided with an arcuate or cam portion 128 which when moved toengagement with a movable contact 130 will cause said contact to engagea stationary contact 132 to complete the circuit through the electricheater 104 and energizes the solenoid valve 108 to move same into openposition to allow the by-pass of refrigerant around the condenser 68 andcapillary tube 26. The movable contact 130 is normally held in upper oropen position by spring 134. However, when the bellows 76 expands andcauses connecting rod 84 to move downwardly, the pawl 122 will engage atooth 124 of wheel 126 to move the wheel a certain distance and afterthe bellows is contracted the connecting rod 84 will move upwardly untilthere is again a demand for refrigeration which causes expansion of thebellows to move downwardly again to cause another movement of theratchet wheel 126. Accordingly, after a predetermined number ofmovements, the cam 128 engages the movable contact 130 to engage contact132 to complete the circuit to the heater 104 and valve 108. It will benoted that when the bellows expands and moves downwardly to causeconnecting rod 84 to rotate the ratchet wheel, the circuit to theelectric motor through contacts 88 and 90 is in closed position topermit the motor-compressor unit to operate. At the time contact 130engages contact 132 the circuit through the electric heater is throughwire 96, contacts 88 and 90, wire 140, contacts 130 and 132, wire 142,heater 104, wire 144, valve 108, a

and wires 148 and 92. Consequently when the heater becomes energized thevalve is simultaneously moved to open position and only during periodswhen the motor compressor unit circuit is closed so that the compressoris in operation during the time the heater is energized and by-pass 108is in open position. While the ratchet wheel and operating mechanismherein shown is diagrammatic, any suitable type of those well known maybe utilized for closing a circuit in response to either thermostaticallyoperated switch or pressure operated switch as is well understood in theart. In addition, the counting mechanism may be of any suitable typethat may be closed upon predetermined movement thereof and opened by anymeans such as a spring 134 or other device which would tend to keep thecircuit open to the heating element and solenoid valve except when thepredetermined movement of the ratchet wheel causes the closing of thecircuit to enable defrosting. In this connection, the arrangement issuch that when the bellows expands, the connecting rod 84 not onlycauses the circuit through the motorcompressor unit to become closed butengages a tooth of the ratchet wheel to close the circuit through theheater and hold it in closed position until the bellows causes theconnecting rod to rotate the ratchet Wheel 126 sufiiciently so that thecam 128 moves free of the contact 130 to allow the spring 134 to raisethe contact to open the circuit to the heater and valve winding.

In Fig. 6 I have shown a modified form of automatic control fordefrosting wherein there is shown diagrammatically a clock or timer usedfor actuating a wheel 162 having a cammed portion 164 which timer may beset so that the cam surface 164 will engage the movable contact 130 onceevery 24 hours to retain the contact 130 in engagement with contact 132for a. predetermined length of time after which the timer will move thecammed portion 164 away from contact 130 to allow the spring 134 to movethe contact 130 away from contact 132 to interrupt the circuit to theheater and the solenoid valve. In this arrangement the timer 160operates entirely independent of the thermostat control 72 which isutilized solely for making and breaking the circuit through themotor-compressor unit. It will be noted, however, that when the contact130 is moved into engagement with contact 132, contact 130 also engagesa contact which is connected by wire 172 with wire 94 and contact 130 isconnected to wire 96 by wire 176 to complete the circuit through themotor-compressor unit so that the motorcompressor unit will be assuredof operation during the period when the heater 104 is energized and thesolenoid valve winding is energized. This takes place regardless ofwhether there is a demand for refrigeration by the thermostat 72 at thetime when the clock or timer completes the circuit through the heatingdevice and by-pass valve. When the cammed portion 164 moves past contact130, the spring 134 will cause contact 130 to move away from contact 170at the same time it moves away from Contact 132 to interrupt the circuitthrough the motor-compressor unit at this point. However, themotor-compressor unit may continue to operate in the event that thethermostat has the contacts 88 and 90 in closed position.

From the foregoing it will be readily understood that I have provided asystem for defrosting a refrigerant evaporator by conducting hot gaseousrefrigerant thereinto wherein it is condensed and the latent heat ofcondensation aids in melting the frost from the evaporator and theelectric heating element vaporizes the condensed refrigerant to causefurther melting of the frost by the heat of evaporation. In this type ofarrangement the evaporator is defrosted in suflicient time to enablefrozen foods stored therein to retain their frozen condition as thedefrosting takes place before such frozen foods begin to thaw.Furthermore, the system is entirely automatic and is arranged so thatthe heating element and the solenoid valve cannot come into operationexcept when the defrosting period takes place and during that period themotor-compressor unit is assured of operation throughout the entireperiod when the heating element and solenoid valve are energized.

Although preferred and modified forms have been illustrated, anddescribed in detail, it will be apparent to those skilled in the artthat various other modifications may be made therein without departingfrom the spirit of the invention or from the scope of the appendedclaims.

I claim:

Refrigerating apparatus comprising a motor-compressor unit, a condenser,a refrigerant avaporator having a liquid accumulator vessel at itsoutlet that contains liquid refrigerant during normal operation, supplymeans for conducting liquid refrigerant from said condenser to saidevaporator, by-pass conduit means between the compressor and evaporatorfor conducting hot gaseous refrigerant directly from the compressor-unitinto the inlet of said evaporator during operation of said unit, heatingmeans adjacent said vessel for applying extraneous heat to the liquidrefrigerant in said vessel of said evaporator only during the operationof said unit and the flow of hot gaseous refrigerant directly to saidevaporator, and conduit means for conducting gaseous refrigerant fromsaid evaporator to said unit.

2. Refrigerating apparatus comprising a motor-compressor unit, acondenser, an evaporator having a liquid accumulator vessel at itsoutlet that contains liquid refrigerant during normal operation, aconduit connecting said unit with said condenser, a supply conduitconnecting said condenser with said evaporator, a vapor return pipeconnecting the outlet of said evaporator with said unit, means forby-passing said condenser and supply conduit to permit direct flow ofgaseous refrigerant into the inlet of said evaporator from said unit, avalve for controlling said means for by-passing, a heating elementarranged in the vicinity of said vessel and in heat exchange relationwith liquid refrigerant in said vessel of said evaporator, and means forcontrolling said valve and said heating element to limit operationthereof during periods of operation of said unit.

3. Refrigerating apparatus comprising a motor-cornpressor unit, acondenser, an evaporator having a liquid accumulator vessel at itsoutlet that contains liquid refrigerant during normal operation, supplymeans for conducting liquid refrigerant from said condenser to said 1%evaporator, conduit means between the evaporator and said unit forbypassing said condenser, a heating element in the vicinity of saidvessel and in heat exchange relation with the liquid refrigerant in saidvessel of said evaporator, and means for initiating the flow ofrefrigerant through said conduit means, the operation of said heatingelement and the operation of said motor-compressor unit at approximatelythe same time.

4. Refrigerating apparatus comprising a motor-compressor unit, acondenser, an evaporator having a liquid accumulator vessel at itsoutlet that contains liquid refrigerant during normal operation, aconduit connecting said unit with said condenser, a supply conduitconnecting said condenser with said evaporator, a vapor return pipeconnecting the outlet of said evaporator with said unit, means forby-passing said condenser and supply conduit to permit direct flow ofgaseous refrigerant into said evaporator from said unit, a valve forcontrolling said means for bypassing, a solenoid for said valve, aheating element arranged in the vicinity of said vessel and in heatexchange relation with liquid refrigerant in said liquid collectingvessel of said evaporator, and means for causing energization of saidsolenoid and said heating element to limit operation thereof duringperiods of operation of said unit.

References Cited in the file of this patent UNITED STATES PATENTS

